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to the procedures of Chen and McGinnis (1981). The results (Table VI) show that there is significantly more xylose; 20.5% (and thus xylan; hence, hemicellulose) in resistant whorl tissue than in susceptible whorl tissue; 13.9%, while the glucose (hence cellulose) content was slightly higher in resistant tissue but probably not biologically important. The presence of the sugars arabinose and mannose is presumptive evidence of two other hemicelluloses, the arabans and the mannans. Thus, the total hemicellulose content was 17.6% for the susceptible line and 24.0% for the resistant line. The difference in the sum of the sugars from 100% can be attributed to proteins, salts, and other non-sugar constituents. The higher analysis for xylose in MpSWCB-1 X Mp496 suggests that xylans may be a source of resistance. Comparable results for sugars in cob, husk, stalk, and leaf were determined by Krull and Inglett (1978) and are also given in Table VI. From this analysis, it can be deduced that cellulose, starch, and xylan polymers are the major sources of residue in corn leaf. Lignin (1.52-1.63%) and salts (analyzed as ash, 4.4-6.4%) evidently contribute only to a limited degree. In summary, the fiber and residue contents are significantly higher in a number of resistant lines. The cellulose and hemicelluloses comprise an important portion of the fiber and can be expected to contribute to leaf toughness, indigestibility, and intractibility to metabolism by the insect. Thus, they evidently explain at least in part a basis of resistance in the cultivars studied. ACKNOWLEDGMENT
We thank Tom Davis and Thomas Oswalt of this laboratory for expert technical service. Registry No. 6-Methoxybenzoxazolinone, 532-91-2; cellulose,
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9004-34-6; hemicellulose, 9034-32-6. LITERATURE CITED Batra, G. K.; Kuhn, C. W. Phys. Plant Pathol. 1975, 5, 239. Chen, C. C.; McGinnis, G. D. Carbohydr. Res. 1981, 90,127. Chippendale, G. M. Environ. Entomol. 1974, 3, 233. Davis, F. M.; Henderson, C. A.; Scott, G. E. J. Econ. Entomol. 1972, 65, 519. Davis, F. M.; Williams, W. P. J. Econ. Entomol. 1980, 73, 704. Guthrie, W. D.; Russell, W. A.; Jennings, C. W., Proceedings of the 26th Annual Corn and Sorghum Research Conference, Chicago, IL, 1971, p 165. Hedin, P. A.; Davis, F. M., USDA, Mississippi State, MS, unpublished data, 1983. Henderson, C. A.; Bennett, S. E.; McQueen, H. F. J . Econ. Entomol. 1966, 59, 360. Hyodo, H.; Uritani, I. Arch. Biochem. Biophys. 1967, 122, 299. Klun, J. A.; Brindley, J. A. J . Econ. Entomol. 1966, 59, 711. Krull, L. H.; Inglett, G., Northern Regional Research Center, USDA, Peoria, IL, personal communication, 1978. Mataumoto, I.; Okazawa, M. Japanese Patent 72 75 593,28 (CA); Chem. Abstr. 1974, 81, 63612. Nicollier, G. F.; Hedin, P. A.; Davis, F. M. J. Agric. Food Chem. 1982, 30, 1133. Robinson, J. F.; Klun, J. A.; Brindley, T. A. J . Econ. Entomol. 1978, 71, 461. Scott, G. E.; Davis, F. M. Agron. J. 1974,66, 773. Sullivan, S. L.; Grocen, V. E.; Ortega, A. Enuiron. Entomol. 1974, 3, 718. Venis, M. A,; Watson, P. J. Planta 1978, 142, 103. Received for review June 17, 1983. Accepted October 28, 1983. Mention of a trademark, proprietary product, or vendor does not constitute a guarantee or warranty of the product by the U S . Department of Agriculture or Mississippi State University and does not imply its approval to the exclusion of other products or vendors that may also be suitable. Mississippi Agricultural and Forestry Experiment Station Journal Article 5537.
Roles of Tobacco Cellulose, Sugars, and Chlorogenic Acid as Precursors to Catechol in Cigarette Smoke Steven G. Carmella,* Stephen S. Hecht, T. C. Tso, and Dietrich Hoffmann Tobacco was extracted sequentially with hexane and methanol-H20, and the extracts were pyrolyzed -at 650 OC in order to identify likely leaf precursors to the tobacco smoke cocarcinogen catechol. The results demonstrated that the methanol-H20 extract and the extracted tobacco residue were good pyrolytic precursors to catechol. Subfractions of the methanol-H20 extract were isolated by HPLC and pyrolyzed. Fructose, glucose, sucrose, and chlorogenic acid were thus identified as important pyrolytic precursors to catechol. Cellulose, a component of the extracted tobacco residue, was also found to be a good precursor to catechol in pyrolysis experiments. To determine the role of these substances as precursors to catechol under the conditions prevailing in a burning cigarette, either [14C(U)]cellulose, [ 14C(U)]fructose,or various levels of the unlabeled polyphenols chlorogenic acid or rutin were added to cigarettes and the mainstream smoke was analyzed for [14C]catecholand catechol. On the basis of these experiments, we estimated the minimum contributions of these compounds to mainstream smoke catechol levels as follows: cellulose, 7-12%; total of fructose, glucose, and sucrose, 4%; chlorogenic acid, 13%; rutin,
